The regulation of bacterial growth and division has been studied in Bacillus subtilis by the analysis of mutants defective in various aspects of the cell cycle. Mutants defective in DNA replication, genome segregation, cell surface growth and cell division have been characterized at the cellular and biochemical levels by techniques appropriate to each particular mutant. Special strains have been constructed which carry combinations of mutants in an isogenic genetic background in order to investigate the interactions of major cell cycle events. Recently, minicell producing mutants have been found. The patterns of growth and cell division, as well as the properties of the anucleate minicells produced by these mutants are currently under study. Our plans for the immediate future include: 1) continued studies of growth and division patterns in various mutants using microscope growth chambers recently developed in our lab and machine analysis with our computer-celloscope apparatus, 2) genetic studies involved with the isolation of new mutants and the construction of specific strains, 3) phage studies in which cell division mutants are used as hosts and infection effects on division are explored, 4) further studies with minicells involving attempts to introduce genetic information into them and 5) immunological studies aimed at identifying mutant defects. The objectives of these studies are to obtain a better understanding of the genetic regulation of cellular growth and division.